The research proposed here will examine the ability of 6, 9 and 16 month old infants to recognize natural categories. Present evidence in this area lacks generalizability to spontaneous behavior due to the predominant use of artificially constructed stimuli (e.g., geometric forms). We propose to assess infants' ability to recognize invariance among non-identical but related stimuli which conform to our definition of a natural category. Two variables of theoretical importance will be examined in order to understand the influences of infant category acquisition: The relative centrality or exemplariness of initial members and the possibility that the object permanence concept is requisite to categorizational ability. To these ends, the following four goals have been identified: 1) Replication of observations of infant categorization (Husaim & Cohen, in press; Cohen & Younger, 1981; Strauss, 1980). 2) Presentation of stimuli from natural categories (e.g., birds) in order to maximize external validity. 3) Examination of the relative influences on category acquisition given a series of very central or exemplary members, as opposed to category acquisition given a series of peripheral, or non-exemplary members. Are these factors important to infants in the same way that they have been shown to be important to children (Hupp & Mervis, 1980) and adults (Homa & Vosburgh, 1976; Rosch, 1973, 1975)? 4) Examination of the possible relationship between object permancenc development (Piaget, 1951; Uzgiris & Hunt, 1975; Corrigan, 1977, 1979) and categorizational ability. Specifically, is object permanence necessary for categorization? Preliminary results strongly support the idea that infants can categorize natural stimuli, at least by nine months. As well, data from our laboratory suggests a relationship between object permanence, categorization, age and sex.